Influence of crystallographic orientation on the recrystallization of pure tantalum through microstructure-based estimation of the stored energy

Abstract

Plastic deformation and static recrystallization of pure tantalum are studied using Electron BackScatter Diffraction (EBSD) technique. Recrystallization kinetics are discussed in light of stored energy estimation from EBSD data acquired on deformed microstructures. Characterization of deformed state reveals the influence of crystallographic orientation on the plastic deformation. Dislocation substructures are formed in the γ-fiber grains and almost no substructures are observed in the θ-fiber grains. Subsequent recrystallization directly inherits this orientation dependence of deformed state. Nucleation is promoted in the γ-fiber grains because of substructure development whereas nucleation is more sluggish to occur in the θ-fiber grains. Thus, a microstructure composed mostly of γ-fiber grains recrystallizes faster than a microstructure with a less strong texture, despite a strain nearly three times lower. At the polycrystalline scale (step size of 1.20 μm in the present case), recrystallization kinetics are better described with stored energy estimated through substructures than through dislocation density. At the substructure scale (step size of 90 nm), Geometrically Necessary Dislocation (GND) density seems to be correctly estimated; still recrystallization kinetics cannot be accounted for by this density because it does not account for the substructure formation.